Hadronic contribution to the photon vacuum polarization: a theoretical estimate
| Autor: | Randy Lewis, Roberto R. Mendel, Bob Holdom |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Quantum chromodynamics
Quark Physics Particle physics Physics and Astronomy (miscellaneous) 010308 nuclear & particles physics High Energy Physics::Lattice Nuclear Theory High Energy Physics::Phenomenology FOS: Physical sciences Constituent quark 01 natural sciences Pseudoscalar meson Gluon Momentum High Energy Physics - Phenomenology High Energy Physics - Phenomenology (hep-ph) 0103 physical sciences High Energy Physics::Experiment Vacuum polarization Nuclear Experiment 010306 general physics Engineering (miscellaneous) Lepton |
| Zdroj: | Zeitschrift für Physik C Particles and Fields. 63:71-76 |
| ISSN: | 1434-6052 0170-9739 |
| DOI: | 10.1007/bf01577545 |
| Popis: | A simple model for the hadronic contribution to the photon vacuum polarization function $\Pi_{had}(q^2)$, for spacelike momenta, is presented. For small momenta, the two loop contribution from the pseudoscalar meson octet is computed from the chiral Lagrangian. The light quark contribution (which at low momentum gives the ${\cal O}(q^6)$ counterterm in the chiral Lagrangian) is calculated within a relativistic constituent quark model incorporating the momentum dependence of the quark mass. The perturbative gluons of QCD are included in a standard fashion. The total result is close to an estimate of $\Pi_{had}(q^2)$ that is obtained directly from $e^+e^-\to hadrons$ data. We further use our results for $\Pi_{had}(q^2)$ to calculate the ${\cal O}(e^4)$ hadronic contribution to lepton magnetic moments and to calculate $\alpha_{QED}(M_Z^2)$. A simpler model of constituent quarks with momentum independent masses gives less favourable results. Comment: 12 pages of LaTeX plus 3 uuencoded postscript figures, UTPT-93-7 |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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